You shouldn't have any problems doing this. We did the haunted carriage ride for Halloween, followed by dinner at WCC, and it was very easy to do both. We even had issues with our carriage ride. Our driver was having problems with the recorder playing the story of sleepy hallow. She ended up having her manager bring over a replacement. I was worried about being late for our WCC dinner. They took our name down and called WCC and told them to seat us no matter how late we arrived. When we got to WCC, not late at all, the hostess knew who we were as soon as I gave her my name. She was like "hey, you aren't late at all". I would book the ride at least 2 hours prior to your WCC ADR, just so that you don't feel rushed.
Last December we did the sleigh ride followed by dinner at Ohana. I scheduled them to be 2 hours apart and we had no issues getting to Ohana on time. We had our own car and drove, but getting to the Poly, or WL, is not hard at all. If going to WL you can take the boat over. There may be a bus route that I'm unaware of. I seem to recall something about a bus route at one time, but not sure if it still (or ever did

) exists. If going to one of the monorail resorts you can take the boat to CR and then catch the monorail.
We thought both the halloween and holiday carriage rides were well worth the price. If I am remembering correctly both were around $60. I think I booked them around the same time I booked ADRS, so 180 days out, but I'm not 100% sure. These two carriage rides are great memories for my family and we'll likely do them again if in WDW around either holiday.